Vacuum cleaners



B. ECK ETAL June 28, 1966 VACUUM CLEANERS ll Sheets-Sheet 1 Filed Aug. 11965 NIK LAUS LAING BY M l 1 X BRUNO ECK ATTORNEYS 55 35 INVENTORS flaJune 28, 1966 B. ECK ETAL 3,257,682

VACUUM CLEANERS Filed Aug. 1, 1963 ll Sheets-Sheet 2 FIG.6

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VACUUM CLEANERS l1 Sheets-Sheet 3 Filed Aug. 1, 1963 INVENTORS BRUNO ASLAING N| OL ATTORNEYS June 28, 1966 B. ECK ETAL 3,257,682

VACUUM CLEANERS Filed Aug. 1, 1965 ll Sheets-Sheet 4 INVENTORS BRUNO ECKN\KOLAUS LAIN BY;% 2

/Q, Z XMMM KTTORNEYS June 28, 1966 B. ECK ETAL VACUUM CLEANERS FiledAug. 1, 1963 1]. Sheets-Sheet 5 INVENTORS BRUNO EGK NI OLAUS LAINZ BY M,I

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VACUUM CLEANERS Filed Aug. 1, 1963 11 Sheets-Sheet 6 FIG 16.

IN V ENTORS BRUNO ECK NIKOLAUS LAING BY/M I ATTORNEYS B. ECK ETAL June28, 1966 v VACUUM CLEANERS ll Sheets-Sheet 7 Filed Aug. 1, 1963PIC-2.22.

s s R 6 H mK N N C R L 0 EE T v S1 mmu M June 28, 1966 B. ECK ETAL3,257,682

VACUUM CLEANERS l1 Sheets-Sheet 8 Filed Aug. 1, 1963 INVENTORS BRUNO EOKo AUS LAING W/ M Ma ATTORNEYS B. ECK ETAL VACUUM CLEANERS June 28, 1966ll Sheets-Sheet 9 Filed Aug. 1, 1963 IN VENTORS BRUNO EGK NIKOLA usLAING M ATTORNEYS June 28, 1966 B. ECK ETAL VACUUM CLEANERS Filed Aug.1, 1963 11 Sheets-Sheet l0 INVENTORS BRUNO ECK NlKOLAUS LAING fiM, I

ATTORNEYS June 28, 1966 B. ECK ETAL 3,257,682

VACUUM CLEANERS ll Sheets-Sheet 11 Filed Aug. 1, 1963 INVENTORS BRUNOECK NIKOLAUS LAING BY/M/ M W/Q, 2% 241m ATTORNEYS inversely related tothe throughput.

United States Patent 91 14 Claims. ((11.15-347) This invention relatesto vacuum cleaners, and is a continuation-in-part of our earlierapplication No. 701,265 now abandoned, filed December 6, 1957. A vacuumcleaner comprises a motor-driven blower which sucks a stream of airthrough a so-called nozzle. In operation the nozzle is applied to asurface to be cleaned so that the dust thereon can be entrained in theair stream. The air is passed through means which separates theentrained dust from the air stream and collects this dust for subsequentremoval.

The present invention, which aims to produce proved form of vacuumcleaner, has regard to the following appreciations:

(a) The air stream has to produce a force on a dust particle whichexceeds its weight and the force with which it adheres to the supportingsurface. The force produced is, on a first approximation, dependent onthe throughput (i.e., the volume of air aspirated per unit of time).

(b) In laminar flow there is always a boundary layer near stationaryobjects, in which the velocity is negligible. The dimensions of thislayer are about those of the dust itself. Thus if the flow is laminarmore suction must be applied to the nozzle than would be necessaryaccording to (a) above had the flow been turbulent.

(c) The relatively massive blower and motor of vacuum cleaners hitheretoknown has either made the-m inconvenient and cumbersome objects to pusharound or has led to the blower, being connected to the nozzle by ahose, which involves great pressure losses.

(d) The blowers previously used have their suction connected to thenozzle by a hose this has meant that the blower has had to producepressures several times higher than what would have been necessary hadthe blower acted directly at the nozzle.

(e) The previously used blowers, operating in the range of low Reynoldsnumbers, are of low efficiency: they require to be driven at high speedto produce the required suction without being intolerably bulky, andthis 1 high speed makes such blowers noisy. A discussion of theoperation of known blowers at low Reynolds numbers will be found inBritish specification No.: 876,611: this British specification howeverwas not published at the date of the application of which this is acontinuation-in-part.

In contrast to the vaccum cleaners known or proposed hitherto, it isstrongly preferred, in carrying out the present invention to make use ofa particular form of cross-flow blower, this blower (called hereinaftertangential blower) comprising a drum-shaped bladed rotor and guide meansco-operating with said rotor to set up a cylindrical vortex when therotor is rotated having a general characteristic of a Rankine vortex,which vortex is eccentric to the rotor axis and guides air twice throughthe path of the rotating blades in a direction transverse to the rotoraxis.

It is to be understood that although cross-flow blowers were known sincethe turn of the century they never found favour commercially apparentlyon account of their unpredictable performance, prior to the developmentWhere the blower is an im- "ice of thetangential blower, certainly sofar as the applicants are aware it has never hitherto been proposed touse a cross-flow blower in a vacuum cleaner.

The tangential blower has several advantages, chief of which is itsability to handle great volumes of air without being bulky or noisy:this enables the blower to be very small by comparison with what hashitherto been regarded as normal. However, the curve of pressure againstvolume drops sharply as the volume is reduced from a critical figure,e.g., by the nozzle becoming blocked. Now a vacuum cleaner, except inspecialist applications, must be able to operate even if the nozzle isblocked: the fact that in the tangential blower pressure and throughputdrop together from a critical value would appear to necessitaterejection of the blower for normal vacuum cleaner applications. Howeverthe invention provides a means of overcoming the problem: nozzle by-passmeans are provided to enable air to flow to the rotor unaffected by thesurface to be cleaned when the resistance to air flow through the nozzlerises above normal by reason of the conjunction of said surface with thenozzle whereby throughput of air through the rotor is maintainedindependent of air flow through the nozzle. Pressure is thereforemaintained although the flow of air through the nozzle drops.

The by-pass can take various forms, as will be apparent from thefollowing description. In certain rather special cases contemplated bythe invention, as where the nozzle is formed between brushes, the nozzleprovides its own by-pass in that air can pass through the bristles ofthe brushes to a sufiicient extent even when the normal opening isblocked.

In the more usual cases where the nozzle is defined by rigid structure,a preferred by-pass means is a duct adjacent the nozzle leading fromambient atmosphere to the suction side of the blower and so positionedas to direct air passing through the duct on to that portion of thesurface to be cleaned which lies beneath the nozzle. When the mouth ofthe nozzle is blocked, sufficient air for the blower enters through theduct to maintain suction. Alternatively, the duct can be supplied with aportion of the air leaving the blower, rather than from the ambientatmosphere, and in this case it is the recirculation of air through theblower which enables suction to be maintained when the nozzle mouth issealed.

Further forms of nozzle by-pass means provided by the invention include:

(a) A duct leading from the delivery side of the blower to the suctionside and operative on slight fall of throughput to provide arecirculating air channel in circuit with the blower.

(b) A diffuser positioned at the outlet of the blower to receive airtherefrom, said diffuser being perforated with the perforations inpressure communication with the suction side of said blower whereby airis removed by the boundary layer suction effect from within the diffuserand is recycled to the suction side of the blower. This by-pass meansconstitutes in effect a special case of (a) above.

(c) A duct opening on the suction side of said blower for passage of airfrom the ambient atmosphere to the blower and wherein the opening ofsaid duct leading to said suction side opposes the direction of air flowfrom the nozzle to the blower, whereby under normal operating conditionsthe dynamic pressure of air moving from said nozzle to said bloweropposes flow of air through said duct, and whereby when said dynamicpressure drops, air will flow through said duct to said blower.

The applicants have found that, unlike the hitherto commonly usedblowers, the tangential blower is a portion Olf the guide means tosensitive to dust; that is its performance may drop sharply in a dustyenvironment. It is accordingly preferred, in accordance with theinvention to arrange the filter means between the nozzle and the blower.It is a further preferred feature of the invention to mount a diffuserat the outlet of the blower, to enable the blower to produce sufficientpressure to suck air through the filter in the required volume.

According to a different aspect of the invention it provides a vacuumcleaner comprising a nozzle adapted to be applied to a surface to becleaned; a motor driven blower having its suction side connected to saidnozzle to direct a stream of air therethrough; filter means to separatedust entrained in said air stream passing through the nozzle and tocollect said dust for subsequent removal; a beater mounted adjacent saidnozzle for contact with the surface to be cleaned and movable inresponse to varying pressure in the air stream; and pressure fluctuationmeans for causing periodic fluctuation of pressure in said air streamwhereby said beater may be moved to effect a beating action on thesurface to be cleaned.

As has been explained, the invention strongly prefers to use atangential blower. With such a blower the pressure fluctuations arereadily produced by arranging move cyclically by reason of forces set upby the air flow through the blower, under the restraint of a spring. Theinvention includes a large variety of further features which, with theirattendant advantages will be described with reference to specificexamples illustrated in the accompanying drawings.

In the drawings:

FIGURE 1 illustrates a vacuum cleaner according to the invention partlyin side elevation and partly in vertical longitudinal section;

FIGURE 2 is a vertical transverse section of the FIG- URE 1 vacuumcleaner taken on the line IIII in that figure;

FIGURE 3 is a plan of the FIGURE 1 vacuum cleaner;

FIGURE 4 is a plan view of a blower forming part of the FIGURE 1 vacuumcleaner, this view showing how air fiow takes place through it inoperation and illustrating the Rankine vortex which forms;

FIGURE 5 is a velocity profile occurring in the FIG- URE 4 blower inoperation thereof;

FIGURE 6 is a velocity profile such as occurs in the prior art;

FIGURE 7 is a diagram illustrative of the Rankine vortex which forms inoperation of the FIGURE 4 blower;

FIGURE 8 is a diagram showing an idealized pattern of flow through therotor of a blower such as that of FIGURE 4, by reason of the Rankinevortex;

FIGURE 9 is a diagram showing the path of a principal flow tube throughthe rotor of the FIGURE 4 blower and illustrating how it impinges on therotor blades; I cross-section of two rotor blades which FIGURE 10 is acan be used in the FIGURE 4 blower;

FIGURE 11 is a graph which shows curves of pressure against volume ofthroughput for the FIGURE 4 blower and for a comparable axial blower;

FIGURES 12 to illustrate nozzle by-pass means which are alternative tothat of the FIGURE 1 vacuum cleaner more specifically;

FIGURE 12 is a plan view corresponding 4 and showing a modified blower;

FIGURE 13 is a partial plan view of a vacuum cleaner showing amodification with respect to that of FIGURES 1 to 4;

FIGURE 14 is a partial vertical longitudinal section of the FIGURE 13vacuum cleaner, taken on the line XIV-XIV in that figure;

FIGURE 15 is a partial plan view of a vacuum cleaner showing a furthermodification with respect to that of FIGURES l to 4;

to FIGURE FIGURE 16 is a graph showing a curve of pressure againstvolume of throughput illustrative of the operation of the vacuumcleaners so far described;

FIGURE 17 is a vertical longitudinal section through the nozzle portionof a vacuum cleaner, illustrating a modification which can beincorporated into the vacuum cleaner of FIGURES 1 to 4;

FIGURES 18 and 19 are sections of a blower generally similar to that ofFIGURE 4 but incorporating fiow control means, each of the two figuresshowing one of two operative positions of the control means and the flowwhich takes place;

FIGURE 20 is a view similar to FIGURE 1 of a modified form of vacuumcleaner incorporating a carpet-beating arrangement;

FIGURE 21 is a cleaner;

FIGURE 22 is a view similar to FIGURE 4 of the blower utilized in theFIGURE 20 vacuum cleaner;

FIGURES 23 and 24 are sections of a blower having a control meansoperable manually to vary flow conditions, the figures showing twooperative positions of the control means and the corresponding flow;

FIGURE 24a is a graph illustrating the operation of what is describedwith reference to FIGURES 23 and 24;

FIGURE 25 is a plan corresponding to FIGURE 3 of a further modified formof vacuum cleaner including means to direct an air jet at a surface tobe cleaned;

FIGURE 26 is a view corresponding to FIGURE 4 and showing the blower ofthe FIGURE 25 vacuum cleaner;

FIGURES 27 and 28 are vertical longitudinal sections showing alternativemeans for controlling the air jet in the FIGURE 25 vacuum cleaner; and,

FIGURE 29 is a side elevation of a battery operated vacuum cleaner.

planof the FIGURE 20 vacuum co-operates with of vanes 10 which extendacross the outlet in a generally longitudinal direction preventing theusers hand or any other sizable object from entering the duct.

The casing 1 is formed on its underside, near the front with lower frontsurface portions 15, 16 merge in a sharply rounded nose 17 situated atnarrowest part of the nozzle Just in [front of the nose 17 a convergentduct 18 opens into the lower front surface portion 16, to lead air in agenerally downward direction towards the surface to be cleaned: the duct18 extends over the whole length of the nozzle 12. The lowest point 19aof the rear hear- .ing surface 14 is somewhat lower than thecorresponding point 19b of the casing surface immediately forward of thenozzle 12.

A dividing wall 20 extends upwardly from the bottom 21 of the casing 1forward of the motor 2, over the whole width of the casing. A filterdesignated generally 22 extends across the casing 1 between the dividingwall 20 filter from getting choked 5. and the top of the front nozzlesurface portion 15, the filter comprises a longitudinally pleated filterpaper 23 supported on wires 23a running longitudinally between thedividing wall and the surface portion 15 and located in the pleats ofthe filter paper.

A shallow dust tray 24 is pivotally mounted at its forward end to thecasing member, designated 25, which, having the form of a bar extendingacross the width of the casing, provides the rear nozzle surface 13 andhearing surface 14: the pivots of the tray are shown at 26, and the trayis shown in full lines in the closed position while chain lines 27 showthe open position of the tray. In the closed position of the tray 24,its rear end 28 engages the forward surface of the dividing wall 20,while its sides 29 engage snugly within the side walls 30 of thecasing 1. The vacuum cleaner is provided with a handle 31 extendingrearwardly and upwardly from a fork the arms 33 of which embrace therear of the casing 1 and are pivoted to it at 34. The forwardextremities of the arms 33 co-operate with leaves 35 at either side ofthe casing 1 which are articulated to lugs 36 rigid with tray 24, sothat the handle 31 can be used to control opening of the tray. The rearends 37 of the levers 35, which are downwardly bent, engage in notches38 at the extremities of the arms. In the normal operating position ofthe arms 33 and tray 24, shown in full lines, the lugs 36 extendupwardly. To move the tray 24 to open position shown by the chain lines27 the arms 33 are moved down to the position shown in chain lines 39.The lever ends 37, being caught in the notches 38, are displacedrearwardly and rotate the lugs 36, which bring the tray 24 with them. Toreturn the tray 24 to closed condition the handle 31 is moved back toits operating position whereupon the levers 35 cause the tray to movecorrespondingly. The tray 24 can thus be emptied without touching it.

The vacuum cleaner, as so far described, operates as follows. Operationof the motor 2 causes the blower, which consists essentially of therotor 3 and the surrounding guide surfaces, to draw in air from thespace 41) above the filter 22 and expel it through the duct 8 to' theoutlet 9, it being understood that the space 41 is always in freecommunication above the filter and around the motor and guide walls 4,5, 6, '7 with the rotor inlet arc 41. This air movement causes a flow ofdust-entraining air into the nozzle 12 and through the filter 22, themain direction of flow through the nozzle 12 is indicated by the arrow42, and it will be appreciated that since the lowest point 1% of thefront bearing surface lies above the corresponding point 1% of the rearbearing surface 14, the bulk of the air will enter from forwards of thenozzle. The static pressure adjacent the nose 17 will be considerablyless than atmospheric, so that a subsidiary stream of air will enter thenozzle 12 through the duct 18 at a good speed. This subsidiary stream ofair is directed at that part of the surface to under the nozzle 12. Theincreased turbulence at the surface to be cleaned improves thelikelihood of a given particle of dust thereon being entrained in theair flow. The subsidiary stream of air is removed with the main streamthrough thenozzle 12. The air entering through the nozzle 12 impingesobliquely on the filter and is channelled rearwardly by the pleats inthe paper 23. Air passes through the filter paper 23 over its wholecomparatively large area: air velocity along the pleats diminishes goingrearwardly so that dust tends to drop out of the air stream into thedust tray 24- below. This, coupled with the fact that air is continuallysweeping over the filter area, rather than impinging upon it at rightangles and passing straight through, tends to keep the with a layer ofdust so as to require frequent changing. It is to be noted that in thearrangement described care is taken to avoid contamination of the filterand consequent deterioration of performance, in contrast in particularto conventional arrangebe cleaned which lies directly 6 merits hithertoused where the dust is stored upon the filter surface.

It will be noticed that even if the surface to be cleaned, a carpet forexample, blocks flow into the nozzle 12, air

can still be drawn through the blower from the duct 18.

The significance of this Will be explained later.

It is also to be noticed that the casing 1 rides over the surface to becleaned without wheels, the bottom 21 of the casing, the bottom of thetray 24, and the bearing surface 14 being well rounded for this purpose.One main factor which makes it possible to do without wheels is therelative small size and weight of the motor-blower combination, forreasons which will appear.

The blower of the vacuum cleaner of FIGURES 1 to 3 will now be describedin greater detail with reference to FIGURE 4, wherein it is shown inmore detail and without other parts, and with reference '-to FIGURES 5to 9 which explain its operation and design.

Referring to FIGURE 4, the blower comprises the cylindrical rotorpreviously referred to and designated generally 3. This rotor has itsinterior entirely clear of obstruction, and is mounted on the shaft ofthe motor 2 (the motor being shown only in FIGURE 1) for rotation aboutits axis at a predetermined speed in the direction of the arrow 52. Therotor 3 is provided with blades 53 extending longitudinally and havinginner and outer edges 54, 55 lying on inner and outer coaxialcylindrical envelopes indicated at 56, 57. The blades 53 are concavefacing in the direction of rotation, and have their outer edges leadingtheir inner edges.

As has already been mentioned, guide walls 4, 5 are provided whichextend the length of the rotor. The guide Wall 4 provides a main guidesurface 59 which divides the suction region S from the pressure regionP. The main guide surface 59 is gently concave with respect to the rotor3 and converges therewith in the direction of rotor rotation from a nose60 to a line of nearest approach 61 so as to define with the rotor aconverging gap 62. The line of nearest approach 61 lies spaced from therotor envelope 57 by more than one third of the radial blade depth (infact by about half), and extends over only a very small arc thereof (infact it subtends at the axis'of the rotor an arc of less than 20).

The ends of the rotor 3 are closed off by discs (not shown) received inrecesses 64, 65 (FIGURE 1) in the upper and lower walls 6, 7 which closeoff the guide walls 4, 5 as already described.

In operation of the FIGURE 4 blower a Rankine vortex is set up, the coreof which is eccentric to the rotor axis, and indicated by the flow linesshown chain dotted at V; the Whole throughput flows twice through therotor blades 53 in a direction always perpendicular to the rotor axis asindicated in general direction only by the chain dotted flow lines F,MF.

FIGURE 7 shows the distribution of velocity in the vortex. The chaindotted line 71 represents a diameter of the rotor taken through the axis72 of the vortex core V: this line 71 as well as the axis 72 is shown inFIGURE 8. Velocity of fluid at points on the line 71 by reason of thevortex is indicated by the horizontal lines 73a, 73b, etc., the lengthof each line 73a, 73b, etc., being a measure of the velocity at thepoint 73a, 73b, etc., respectively. The envelope of these lines is shownby the curve 74, which has tWo portions, one 74a approximately arectangular hyperbola and theother, 74b, a straight line. The curve 74arelates to the field region of the vortex and the curve 74b to the coreregion. The direction of flow within the rotor is shown for the variousflow lines F in FIGURE 8. where the core region is shaded, and theremaining flow lines are those of the field region.

The core V of the vortex is a whirling mass of air with no translationalmovement as a whole, and velocity diminishes going from the periphery ofthe core to its axis 72. Static pressure along the line 71 is shown bythe curve 75: it will be seen that the vortex core V is a region of lowpressure. The location of the core region can be discovered byinvestigation of pressure distribution within the rotor.

It will be understood ideal or mathematical conditions will onlyapproximate to those curves. as will be seen, FIGURE 4 does notcorrespond exactly with FIGURE 8. Although for convenience the vortexcore V has been shown circular and has been regarded as possessing anaxis, the core will usually not be truly circular.

The velocity profile of the air at the second entrance thereof to therotor blades will be that of the vortex. In the ideal case of FIGURE 7this profile will be that of the Rankine vortex there shown by curves74a, 74b; in an actual case the profile will still have the generalcharacter of a Rankine vortex. Thus there will be in the region of theperiphery of the core V a flow tube of high velocity indicated at MP inFIGURES 4 and 8 by the heavier chain dots while the flow tubes remotefrom the periphery of the core will have a very much smaller velocity.On account of the vortex there is at the exit from the rotor 3 avelocity profile such as shown (somewhat exaggerated) in FIGURE 5 wherethe line PQ represents the exit arc 63 and the ordinates representvelocity.

that the curves are those of an Rankine vortex and actual flow In fact,

The curve exhibits a pronounced maximum at R which is much higher thanthe average velocity represented by the dotted line (the average beingobtained by dividing the total throughput per unit of time by the arearepresented by the exit are 63).

It will be appreciated that much the greater amount of air flows in theflow tubes in the region of maximum velocity. It has been found thatsome 80% of the flow is concentrated in the portion of the outputrepresented by the line ST, which is less than 30% of the total are 63.A much smaller arc is in fact all that needs to be considered. A normalvelocity profile for'fluid flow in a defined passage is shown by way ofcontrast in FIGURE 6: those skilled in the art will regard this as anapproximately rectangular profile. This is the sort of profile which,following the principles generally adhered to in the art hitherto, adesigner of a flow machine would aim for in the outlet thereof.

The maximum velocity R as shown in FIGURE 5 appertains to amaximum-velocity flow tube indicated in FIGURES 4 and 8 by the heavierchain dots and designated MF. With a given construction the physicallocation of the flow tube MF is fairly closely defined. Therefore in therestricted zone of the rotor blades 53 through which this flow tube MFpasses, the relative velocity between blades and fluid is much higherthan it would be in a flow machine which, following the principlesadhered to hitherto in the art, was designed for a rectangular' velocityprofile and uniform loading of the blades in the zones thereof wherefluid passes.

One main advantage of the blower described will now be appreciated. Asthe velocity of the flow tube MF is several times greater than theaverage velocity (see FIG- URE 5), in the restricted blade zones throughwhich the flow tube MF passes there will be much less separation lossthan if that tube flowed at the average velocity of throughput; in theflow tube MF, that is, transfer of momentum to the air occurs underexcellent conditions. The transfer of momentum in the flow tubestravelling below the average velocity will be poorer, but on balancethere is a substantial gain because by far the greater proportion of thethroughput is associated with the flow tube MF.

A blower for a domestic vacuum cleaner is necessarily a flow machineoperating at low Reynolds numbers. In the past low Reynolds numbers havebeen associated with unavoidable inefliciency. However in the blowerdescribed, despite an overall low Reynolds number, a major portion ofthe flow is in fact at high Reynolds numbers owing to its velocity beingfar above average. Thus this blower is able to show unexpectedly highefliciencies and in consequence, for a corresponding performance ablower constructed on the principles described above will be smaller andlighter than a comparable axial or centrifugal blower of conventionaldesign.

FIGURE 9 shows the maximum velocity flow tube MF intersecting theenvelope 56 at 80, 81. It will be seen that ideally the maximum velocityflow tube MF undergoes a change of direction of about in passing throughthe interior of the rotor, and that the major part of the throughput(represented by the flow tube MF) passes through the rotor blades wherethey have a component of velocity in a direction opposite to the maindirection of flow within the rotor indicated in FIGURE 9 by the arrow A.

Vector diagrams are shown in FIGURE 9 for the velocities at the points80, 81. In the diagrams U is the velocity of the inner edges of theblades at the points 80, 81 respectively, VA the absolute velocity ofthe air in the flow tube MF at these points, and VR 1 and VR 2 thevelocity of that air relative to the blade at these points as found bycompleting the triangles. The rotor blade angles can be designed forshock-free flow of the maximum flow tube MF since, as shown above, itflows through narrowly defined zones of the rotor.

It is considered that the blade angles and blade curvature determine thecharacter of the vortex while the position of the vortex core isdetermined by means of the main guide surface 59. It is considered thatin a given case the particular blade angles and blade curvature, dependon the following parameters among others: the diameter of the rotor, thedepth of a blade in radial direction, the density and viscosity of thefluid, the dispositions of the external guide body, the rotational speedof the rotor, as well as on the ratio between overall pressure and backpressure. These parameters must be adapted to correspond to theoperating conditions ruling in a given case. This teaching is notlimited to a particular case but is quite general: nevertheless in agiven case the teaching given imposes the adoption of quite definiteblade angles and curvature. (Blade curvature is in this connection to beunderstood to mean not only the curvature of a blade of uniformthickness, but also the curvatures of the contours of profiled blades).Whether or not the angles and curvatures have been fixed at optimumvalues is to be judged by the criterion that the flow tubes close to thevortex core should be deflected by approximately 180.

Reverting to FIGURE 4, it will be seen that the guide wall 4 provides afurther guide surface 83 merging with the main guide surface 59 at thenose 60. The flow tube MF tends to follow the guide surface 83, just asthe vortex core V tends to adjust itself to bring its peripheral flowtube parallel to the main guide surface 59.

The guide wall 5 diverges steadily from the rotor 3 going from a line 84of nearest approach thereto which lies opposite the main guide surface59. The line 84 of nearest approach lies spaced more than one third theradial blade depth from the rotor envelope 57, in fact (like thecorresponding line 61 of the main guide surface 59) about half thatdepth. The arcs of entry to and discharge from the rotor 3 divide at theline 84, the former being over 180 in extent.

The preceding discussion will have indicated that the most importantguide surface is the main guide surface 59 and that the blower willoperate even if the surface 83 and the wall 5 are absent. Although theillustrated configuration of the surface 59 is thought to be theoptimum, other guide surface configurations are possible, including arounded nose and a surface parallel to and spaced from the rotorenvelope 57 and defining therewith a parallel gap in contrast to theconvergent gap 62 illustrated. In contradistinction to cross-flowmachines hitherto proposed, it is strongly preferred that the surfaceswhich lie close to the rotor 3 should at their nearest apa,257,es2

9 proach be well spaced therefrom: this not only reduces noise andfacilitates manufacture, but improves efficiency as well.

The design of the rotor blades 53 is complicated by the fact that eachflow tube passes twice over each blade, first inwardly, then outwardly.FIGURE 10 shows one preferred form of rotor blade, which canconveniently be moulded in a plastics material. The blades,heredesignated 85 are characterized by being thickened adjacent theirinner edges: this thickening, besides increasing turbulence, reduce theshock at entry to the blades of the lower-velocity flow tubes. Furtherincrease of turbulence can be obtained by flutings or grooves or otherflowdisturbing irregularities at inner and/or outer edges of the blades.One such fiuting is shown at 86.

FIGURE 11 shows curves contrasting the operation of a blower such asdescribed with reference to FIGURES 4 to 9 with known vacuum cleaner bloers. The throughput volumes are plotted as abscissae and the suction(pressure below atmospheric) as ordinates. Curve 9% represents theresistance of a given apparatus with clean filter, and curve 1 theresistance of the apparatus with the filter loaded. Curve 92 representsthe characteristic (i.e., relationship between pressure and throughput)for a blower as described with reference to FIGURES 4 to 9. Theoperating range of throughput is shown hatched: the loading up of thefilter effects a reduction of throughput as shown at 93 and an increaseor" suction as shown at 94. The maximum operating pressure is only verylittle below the maximum pressure 95 of which the blower is capable. Bycontrast, curve 96 shows the characteristic of a blower of known type:here the operating pressures are far below the maximum pressure @7 whichthe blower can develop.

It has already been mentioned as one of the appreciations on which thisinvention is based, that the capacity of a vacuum cleaner to remove dustparticles is dependent largely on the throughput. With the known blower,high pressure at the point 97 is nearly useless as the throughput isvery small. Yet, it is necessary to use a blower which can produce thispressure in order to have the operating range illustrated.

Now one of the characteristics of the blower according to FIGURES 4 to 9is that the pressure falls to nearly zero as the throughput drops belowthat of he maximum pressure point 95. Thus if such a blower were to bemounted in a vacuum cleaner without special precaution and the nozzlewere to be blocked, as by some impermeable sheet material, throughputand pressure would fall together, and the vacuum cleaner would for thetime being cease to operate effectively. It will usually be desirable toprevent this from happening.

FIGURE 1 illustrates one way to prevent the throughput from fallingunduly. Thus, the duct 18 provides a bypass for air flow towards therotor 3 when the mouth of the nozzle 12 is blocked by a carpet or thelike. This in fact is the primary object of the duct 13; itsturbulencecreating effect is valuable, but secondary.

Alternative nozzle by-pass arrangements are shown in FIGURES 12 to 14.Thus, should it be desired to dispense with the by-pass duct 18 ofFIGURE 1, the dittusing outlet duct 8 of that figure could be replacedby the difiusing outlet duct 16% of FIGURE 12 which is perforated, asshown at 101, in those regions where separation of the boundary layer islikely to occur; in other respects the vacuum cleaner remains similar tothat of FIGURE 1. In operation, when the nozzle 12 (not shown in FIG-URE 12 but illustrated in FIGURE 1) becomes blocked the pressure in thespace 4%) drops: this is the pressure immediately outside the perforateddiffusing duct 1%, so that the boundary layer is sucked out through theholes 101 and recirculates through the rotor 3. The walls of the duct1%, or parts of them, can be made of fabric.

A generally similar effect can be obtained with an inlet duct on thesuction side of the rotor 3 downstream of the nozzle, as shown at 103 inFIGURES 13 and 14: it is to be understood that these figures show onlythe rear portion of a vacuum cleaner which is generally similar to thatof FIGURES l to 3 except as regards the omission of the duct 18 showntherein and the presence of the duct 103. Similar parts are given thesame reference numerals and will need no further description.

The duct 103 is formed as a slit in the rear wall 104- of the casing 1,a lower portion 105 of this wall overlapping an upper portion 106thereof in outwardly spaced relation thereto. When the nozzle of thevacuum cleaner is blocked the pressure drops in the space 107 betweenthe motor 2 and the rear casing wall 104, and air flows into that spacethrough the duct throughput to the rotor 3, the inward flow beingopposite in direction to the flow through the space 107. The duct 103 isdesigned so that in normal operation there is a balance between thedynamic pressure of the air in the space 107 which fiows up to the rotor3, and the difference between the static pressure in the space 107 andthe ambient pressure: thus in normal operation there is negligible flowthrough the duct 103.

If it is required to increase the flow velocity in the space 107,partition walls 108 may be formed in the casing 1 between the side walls30 thereof and the motor 2 and guide walls 4, 5, so as to constrain allthe air from the space 413 to pass around the lower part of the motor.

The FIGURE 15 bypass arrangement comprises a duct 111 at the narrow endof the diffusing outlet duct 8 and providing communication between thelatter duct and the space at). The guide wall 4 is made in two parts111, 112, the first providing the main guide surface 59 and an initialportion of the guide surface 83; the second guide wall part 112 providesthe remainder of the surface 83 and overlaps the part 111 in outwardlyspaced relation to form a part of the duct 11!). The guide wall 5 issimilarly divided into two parts 113, 114 which overlap to provide afurther part of the duct 110. The upper and lower duct walls 6, '7 aresimilarly divided, so that the duct extends all around the duct 8.

The bypass duct 110 is substantially inoperative when the vacuum cleanernozzle 12 is open, but when the nozzle becomes blocked the pressure inthe space 4% drops and air is drawn into it from the duct 8 through theduct 111 and this air is recycled through the rotor 3 to maintain, tosome degree, the throughput of the blower.

Once again it is to be assumed that the FIGURE 15 vacuum cleanerresembles that of FIGURES l to 3 except for the substitution for thebypass duct 18 of the duct 111).

The effect of the nozzle bypass arrangements of FIG- URES 1 to 3, 12,13, 14 and 15 is illustrated in FIGURE 16, in which values of throughputthrough the nozzle 12 are plotted as abscissae, and pressure values asordinates. The curve illustrates the relation of pressure and throughputfor the blower of FIGURE 4 without a bypass arrangement, and the dottedline 121 shows the effect of introducing the bypass. The curve showshow, without the bypass, progressive blockage-of the nozzle andconsequent decline in blower throughput causes a characteristic fall inpressure from the maximum 122 to a low value. (This characteristicpressure fall has been men tioned earlier in connection with FIGURE 11.)By contrast, with a bypass arrangement the blockage of the nozzle doesnot cause more than a slight drop of blower throughput so that, as shownby curve 121, pressure is substantially maintained. This enables thevacuum cleaner to continue functioning efficiently despite occasionalpartial or complete blockages of the nozzle thereof.

It is to be understood that the various nozzle bypass arrangements canbe used in various combinations if desired. Various further bypassarrangements are discussed with reference to later figures.

FIGURE 17 shows a modification of the front portion of the vacuumcleaner of FIGURES l to 3: it is to be as- 1tl3 so as to provide I Isurned that the parts of the vacuum cleaner not illustrated in FIGURE 17are substantially similar to those of FIG- URES 1 to 3.

FIGURE 17 shows a nozzle designated generally 130 having a series ofprojections 131 about the nozzle mouth 132; restricted air inletopeningsare provided between adjacent such projections. The vacuum cleanercasing, here designated 133 provides a wall 134 at the left hand side ofthe nozzle 130, which is thickened as shown at 135 and there formed withan opening 136 closable by a pivoting flap 137. The friction at thepivot of the flap 137, indicated at 137a, is such that the flap canreadily be adjusted by hand, but will remain in adjusted position innormal use of the vacuum cleaner. In the closed position of the flap 137(shown in chain lines) its inner surface 138 fairs more or less with therest of the interior of the nozzle: this position is suitable forcleaning material that is readily air-permeable, for example lightweightcurtains-in such use the throughput will never be unduly reduced. Theposition is also suitable for cleaning a rigid surface such as a floorwhich cannot close up the inlet openings between the projections 131.For nonpermeable and semipermeable flexible materials the flap 137 isopened: the best opening for any material to'be cleaned can be found byexperiment. When the flap is open, the outer surface 139 thereof defineswith 'the opposed side 140 of the opening 136 a convergent duct leadingair downwards to the nozzle mouth 132 as shown by the arrows 141: itwill be understood that air enters the opening 136 because, as entry ofair past the projections 131 is restricted, the interior of the nozzleis a zone of low pressure. The air entering the opening 136 has a highvelocity on account of the converging of the surfaces 139 and 140between which it enters (as is also the case of the duct 18 of FIGURE1), and it impinges on a portion 142 of the surface 143 to be cleaned atthe middle of the nozzle mouth 132. This creates a powerful whirling ordisturbance of the dust as indicated at 144, the disturbance tending toextend over the whole area of the nozzle mouth 132 by reason of theangle at which the air enters the opening 136.

The effect of the air entering the opening 136 at the angle shown is toobviate sluggishness in the removal of dust due to laminar flow in thenozzle mouth 132 as previously referred to. It will be seen that thegeneral configuration of nozzle 130 and opening 136, with the flap 137positioned as shown, is generally similar to that of the nozzle 12 andduct 18 in FIGURE 1: the two arrangements operate similarly as regardsthe stirring up of dust, and the provision of a bypass to maintain rotorthroughput should the nozzle become blocked. As above mentioned, incontrast to that of FIGURE 1, the FIGURE 17 arrangement provides forclosing the bypass in the special cases where the surface to be cleanedis such as to be incapable of blocking the nozzle.

As previously explained in a blower such as described with reference toFIGURES 4 to 9 the throughput and pressure depend on the character ofthe vortex and its location with respect to the rotor blades, and thisin turn depends on the character and location of the main guide surface,designated 59 in FIGURE 4. FIGURES 18 and 19 show a modified blowerconstruction in which the effective main guide surface can be altered,to vary the throughput and pressure.

The blower of FIGURES 18 and 19 makes use of a rotor similar in allrespects to the rotor 3 of FIGURE 4: the same reference numerals will beused for corresponding parts which will need no further description. Theblower of FIGURES l8 and 19 employs a guide wall similar to the guidewall of FIGURE 4, and similarly designated, but instead of the wall 4thereof the vortexstabilizing arrangement takes the form of a guide bodydesignated generally 150 extending the length of the rotor 3 oppositethe wall 5 and defining therewith the outlet duct here designated 151.

- core, and is quieter, but

The guide body comprises a fixed portion 152 presenting a wall surface153 to the duct 151 which surface is continued towards the blower in awall 156 of sheet material whose free end portion is spaced somewhatfrom the rotor. The guide body 150 further comprises an auxiliary body158 which is generally triangular as seen in section and is pivotedabout an axis parallel to one edge of the wall 156 so that its curledend portion 157 forms a continuation of the end of wall 156 on the entryside thereof, the pivot axis being indicated at 159. The body 158 hasone concave side 160 opposite the rotor. In the FIGURE 18 position ofthe body 158 the concave side 160 thereof converges towards the rotor 1in the direction of rotation by way of continuation of the curled endportion 157 of the body 158: thus a wedge-shaped space 161 is formedbetween the surface 160 and rotor 3 and a vortex core is consequentlyset up as shown at V. In the FIGURE 19 position the body 158 isretracted behind the wall 156 and is inoperative; in this position thevortex is formed at the curled portion 157 of the body 158 as shown.Thus the vortex core is displaced towards the outlet.

In the FIGURE 18 arrangement the configuration of the flow guidingsurfaces is generally similar to that of FIGURE 4, and the main guidesurface is the surface 160: the FIGURE 19 arrangement is different andthe main guide surface is the curled tip 157 of the body 158. The FIGURE18 arrangement produces a bigger vortex produces less throughput. Theconstruction may thus be used normally in the FIGURE 18 arrangement, andthe body 158 moved to the FIG- URE 19 position when the character of thesurface to be cleaned requires extra throughput.

FIGURES 20 to 22 show a modification of the vacur um cleaner of FIGURES1 to 3, designed to produce a beating effect on a carpet 169 to becleaned. Parts which correspond to those of FIGURES l to 3 are given thesame numerals and will need no further description.

The vacuum cleaner of FIG'URES 20 to 22 has no duct 18 opening into thenozzle 12, as in FIGURE 1, but instead employs the perforated-diffuserbypass arrangement described with respect to FIGURE 12.

Instead of the dust tray, here designated 24', being pivoted at itsforward end it is pivoted to the side walls 30 of the casing 1 by meansof lugs 170 adjacent its rear end. The sides of the tray 24' fit snuglywithin the casing walls 30 as shown in FIGURE 2; the forward end of thetray is adapted to slide with minimum friction over acorrespondingly-shaped surface 171 of the casing member 25 so as to forma substantially airtight joint therewith, and the rear edge of the traycarries a rubber bead 172 in sealing relation with the casing wall 20.The tray 24' is connected adjacent its forward end with the casing bymeans of a spring 173. The tray 24 is thus capable of oscillation underthe influence of pulsating air pressure in the space above it.

To empty the tray 24' of dust the spring 173 is disconnected from thetray which is then pivoted downwardly by hand. The emptying arrangementof FIG- URE 1 is not employed to the vacuum cleaner of FIG- URES 20 to22.

Pulsating pressure in the space above the tray 24 is produced by theblower shown in FIGURE 22. This blower employs a rotor 3 and guide wall5 similar to those of FIGURE 4, similar references denoting similarparts. However, in place of the guide wall 4 of FIGURE 4 there isprovided a guide means designated generally 174 extending the length ofthe rotor between upper and lower walls (not shown in FIGURE 22) andcomprising a main body 175 which is fixed and an auxiliary body 176which is pivoted about the axis 177 and connected thereto by a spiralspring 178. Comparing this arrangement with that of FIGURES l to 4, itwill be seen that while the main body 175 provides a fixed guide surface179 corresponding to the surface 83 (FIGURE 4) it is the auxiliary body176 which provides the main guide surface here designated 13%) whichcorresponds to the surface 59 of FIGURE 4, and that unlike the surface59, the surface 180 is movable relative to the rotor.

In operation, the auxiliary body 176 performs weakly damped oscillationsunder the influence of forces set up by the moving air, and under thecontrol of the spring 178. From the foregoing it'will be appreciatedthat movement of the main guide surface (here shown at 130) effects thevortex and hence the pressure and throughput produced. Thus theoscillations of the body 176 cause pressure pulsations which, by theireffect on the tray 24' cause it to move up and down and thereby producea beating effect on the carpet 169. This effect is enhanced by raisingthe mouth of the nozzle 12 as compared with FIGURE 1: the carpet 169will tend to lift to the nozzle, and the tray 24' will periodicallyagitate the lifted part of the carpet.

FIGURES 23, 24 and 24a illustrate a further modification of the vacuumcleaner of FIGURES 1 to 3. It is to be assumed that the modified blowerof FIGURES 23 and 24 is incorporated in FIGURES 1 to 3 in place of theFIGURE 4 blower, without other modifications. Parts in FIGURES 23 and 24which correspond with parts of the FIGURE 4 blower are given the samereferences and will need no further description.

Once again it will be seen that the blower of FIGURES 23 and 24 employsa rotor 3 and guide wall 5. However the guide wall 4 of FIGURE 4 isreplaced by adjustable guide means. These guide means include a rigidwall 191) opposite the wall 5, and a generally triangular-sectionedmovable body 191 pivoted to the wall 191! by means of a sheet of rubber192 which is secured thereto in overlying relation and which is securedalso to the body 191; the sheet of rubber 192 is recessed into a guidesurface 193 of the body 191 and provides a fairing between it and thatsurface in all positions of the body 191. The guide surface 193 liesopposite the guide wall 5, and merges at a rounded nose 194 into afurther guide surface 195 which lies opposite the rotor 3. A strip 1% ofrubber is secured at one edge to a bar 197 lying parallel to the rotorand somewhat spaced therefrom so that the opposite edge 198 of thestrip, which is bevelled,

. presses against the guide surface 135 in all positions of the body191. By means of a lever 199 the body 191 can be moved between thepositions shown in FIGURES 23 and 24. In the FIGURE 23 position of thebody 191, the rubber strip 1% and the upper part of the body surface 195combine to form a main guide surface corresponding to the surface 59 ofFIGURE 4, but of greater extent: the vortex core V which forms is oflarge size. In the FIGURE 24 position of the body 191 the main guidesurface is provided solely by the rubber strip 196 the upper edge 1% ofwhich touches the body at the nose 194 thereof: the extent of the mainguide surface is small, and the vortex core V is correspondingly small.The throughput of the blower is much greater in the FIGURE 24 positionof the body 191.

FIGURES 23 and 24 illustrate only diagrammatically the mechanism formoving the body 191. The lever 199 connected thereto is articulated to arod 260 extending from one end wall 2131 of a bellows 202 having itsother end 2113 fixed and its interior connected to a squeeze bulb 204mounted on the vacuum cleaner in any convenient position, e.g., the topof the handle 33. The bellows 2112 has a bleedoff of predetermined size,shown by the capillary 205. When the bulb 2&4 is squeezed by hand, thebellows 202 expands and brings the body 191 from its normal positionshown in FIGURE 23 to its FIGURE 24 position. Release of the bulb 2&2returns the body to the FIGURE 23 position. If the bulb 204 is keptsqueezed, the body will return slowly to the FIG- URE 23 position byreason of the bleed capillary 205.

FIGURE 24a illustrates the operation of what has been described withreference to FIGURES 23 and 24.

This figure shows a curve 210 of efficiency (1;) against throughput(g5), and a curve 211 of power taken (N) against throughput: efficiencyand power are represented as ordinates, and throughput as abscissae. Thenormal operating point is shown at 212. Now reducing the throttling asdescribed brings the operating conditions to the point 213. Thethroughput is much increased and so is the power taken, while theeificiency is about the same. The increase in throughput corresponds (aspreviously explained) to increased ability to pick up dust, the increasein power consumed is accounted for over a short period by the kineticenergy stored in the motorrotor combination, which in this case ispreferably pro-' vided with a flywheel. Operation for any appreciabletime at the point 213 would lead to damage of the motor throughoverload. It is for this reason the bellows 202 is provided with thebleed 205.

Instead of pivoting the body 191 to control the blower, a similarcontrol can be exercised by pivoting the guide wall 5 about an axis atits line of nearest approach to the rotor.

The arrangement shown enables the sucking ability of a vacuum cleaner tobe momentarily increased under convenient manual control, for example topick up a thread on a carpet.

The FIGURE 1 nozzle (reference numeral 12) is provided with a duct 18through which a stream of air enters from the surrounding atmosphere andstirs up dust directly under the nozzle to facilitate its being suckedin. FIGURES 25 to 27 show .a vacuum cleaner in which a stream of air forthis purpose is supplied from the blower. Parts of the vacuum cleanerwhich correspond to parts described with reference to FIGURES 1 to 3 aregiven the same reference numerals and will not be discussed.

The front of the vacuum cleaner (FIGURES 25 and 27) is formed with aduct 2211 in the thickness of the casing 1 which leads from a point 221towards one side of the upper part of the casing down to the nozzle 12which it enters similarly to the duct 18 of FIGURE 1: the duct fans outfrom the point 221 so as to enter the nozzle over the whole lengththereof. The duct 220 is supplied with air from a blower shown in detailin FIG- URE 26 and which differs somewhat from that illustrated withparticular reference to FIGURE 1. This blower makes use of a rotor 3 andguide wall 5 similar to those of FIGURE 1, but for the guide wall 4substitutes vortex-stabilizing means in the form of a main and anauxiliary guide body 222, 223 respectively, the peripheral fiow tubes ofthe vortex core V circulating around the latter. The side of the mainguide body 222 facing the guide wall 5 fairs into a side wall 224diverging with respect thereto. The outlet duct defined between thewalls 224 and 5 is subdivided by curved partition walls 225, 226 and 227into three large channels 228,229, 230 receiving the slower flow tubesfrom the rotor 3 and discharging through the outlet 9, and a separatechannel 231 leading past the outlet into the duct 220, and fairingthereinto at the point 221. The purpose of dividing flow to the outlet 9is to reduce losses in the conversion of kinetic to pressure energy dueto the widely different velocities at which the different stream tubesenter the diffusing outlet duct. The function of the channel 231 is tocollect the fastest-flowing stream tubes adjacent the vortex core V (inthis case a minor proportion of the total flow) and to feed this airstream to the duct 220 where a partial conversion of the kinetic energyto pressure occurs.

The recycling to the nozzle 12 of a minor proportion of the total rotorthroughput provides a by-pass flow when the mouth of the nozzle isblocked by the surface to be cleaned, and so enables the blower tomaintain adequate suction, as previously explained.

It is undesirable that a stream of air should continue to pass out ofthe duct 220 when the vacuum cleaner is lifted off the carpet, sincethis would tend to scatter dust. To close the duct 220 under theseconditions a portion 232 of it adjacent the point 221 is made ofresilient material such as rubber; the cranked upper end 233 of :avertical rod 234 slidably mounted in the casing 1 overlies the flexibleduct portion 232 While the lower end of the rod is connected to theupper side of a diaphragm 235 fixed in the casing 1 above the filter 22.When the vacuum cleaner is lifted off the floor, the pressure rises inthe space above the filter 22, the diaphragm collapses, and the rod 234slides down to pinch off the duct portion 232.

An alternative method of blocking the duct 220 is shown in FIGURE 28:here instead of the diaphragm 235 the rod 234 is connected to a castor236 which in normal operation runs over the surface to be cleaned andholds the cranked end 233 of the rod 234 off the flexible duct portion232. The rod 234 drops and pinches the duct portion 232 shut under theinfluence of the tension spring 237 when the castor 236 comes off theground.

FIGURE 29 illustrates a miniature vacuum cleaner having all the featuresillustrated in FIGURES l to 3,

except that they are on a smaller scale. The various parts aredesignated by the same numerals as used in FIGURES 1 to 3, and will notneed further description. However, in place of connecting the motor 2 toa main supply, the casing 1 is extended rearwardly and provided with adetachable end portion 460 to accommodate, and provide for access to, abattery 461 supplying power for the motor.

We claim:

1. A vacuum cleaner comprising a handle and a cleaner head adapted to bepushed over a surface to be cleaned, said cleaner head having a casingwith an upper surface and substantially fiat bottom surfaces adapted toslide over the surface to be cleaned, a motor in said casing, a blowerof the cross-flow type in said casing attached at one end to the shaftof said motor with said blower having a drum-shaped bladed rotor, saidrotor being vertically positioned in said casing where-in thelongitudinal axis of said blower is vertical, a nozzle in said casingadapted to slide over the surface to be cleaned and being connected tothe suction side of said blower, an outlet in the upper part of saidcasing connected to the outlet of said blower and being at substantiallythe same height as the end of said blower opposite said motor so thatthe over-all height of said cleaning head is substantially equal to theover-all height of said motor and attached blower, collection means insaid cleaner head for collecting dust for subsequent removal from saidcleaner head, filter means in said cleaner head to separate dustentrained in the air passing through said nozzle, and nozzle bypassmeans through which air flows to the rotor unaffected by the surface tobe cleaned when resistance to air flow through the nozzle exceeds apredetermined level by rea' son of the conjunction of said surface to becleaned with the nozzle whereby throughput of air through said rotor ismaintained independent of air flow through said nozzle.

2. A vacuum cleaner as claimed in claim 1 wherein the nozzle bypassmeans includes a duct adjacent said nozzle leading from ambientatmosphere to the suction side of said blower.

3. A vacuum cleaner as claimed in claim 2 wherein the opening of saidduct leading to the inlet of said blower is positioned adjacent saidnozzle to direct air passing through said duct onto that portion of thesurface to be cleaned which lies beneath the nozzle.

4. A vacuum cleaner as claimed in claim 1 wherein the nozzle bypassmeans includes a duct leading from the delivery side of said blower tothe suction side thereof.

5. A vacuum cleaner as claimed in claim 1 wherein said nozzle bypassmeans includes a duct opening on the suction side of said blower forpassage of air from the ambient atmosphere to the blower and wherein theopening of said duct leading to said suction side opposes the directionof air flow from the nozzle to the blower, whereby under normaloperating conditions the dynamic pressure of air moving from said nozzleto said blower opposes fiow of air through said duct, and whereby whensaid dynamic pressure drops, air will flow through said duct to saidblower.

6. A vacuum cleaner as claimed in claim 1 having in addition a diffuserpositioned at the outlet of the blower to receive air therefrom, saiddiffuser being perforated with the perforations in pressurecommunication with the suction side of said blower whereby air isremoved by the boundary layer suction effect from within the diffuserand is recycled to the suction side of the blower.

7. A vacuum cleaner as claimed in claim 1 wherein said filter means islocated within the air stream passing from said nozzle to said blower.

8. A vacuum cleaner as claimed in claim 7 wherein said filter means ispositioned above said collection means whereby dust-entrained airimpinges upon the bottom of said filter and falls therefrom into saidcollecting means.

9. A vacuum cleaner as claimed in claim 8 wherein said collection meanscomprises a tray located adjacent said nozzle.

10. A vacuum cleaner as claimed in claim 9 wherein said tray ispivotally connected at one end to said vacuum cleaner whereby its otherfree end may move between dust-catching and dust-releasing positions.

11. A vacuum cleaner as claimed in claim 10 wherein said filter means ispleated to increase its effective area, said pleats extending in adirect-ion to guide airpassing from said nozzle over said collectionmeans.

12. A domestic vacuum cleaner comprising a handle and a cleaner head tobe pushed over a surface to be cleaned: the cleaner head having a casingwith smooth outer surfaces including bottom surfaces adapted to slideover the surface to be cleaned and providing a nozzle adapted to beapplied to a surface to be cleaned; a motor driven blower in the casinghaving its suction side connected to said nozzle and arranged to draw astream of dust-entraining air through said nozzle, said blower having avertically positioned drum shaped bladed rotor and guide means includinga guide wall extending the length of said rotor and cooperating withsaid rotor to form a cylindrical vortex when said rotor is rotatedhaving a general characteristic of a Rankine vortex which vortex iseccentric to the rotor axis and which guides air twice through the pathof the rotating blades in a direction transverse to the rotor axis; amotor connected to the lower end of said rotor; an outlet in the upperpart of said casing connected to the outlet of said blower and being atthe same height as the upper end of said rotor; large area dust filtermeans located in said casing between the nozzle and the blower toseparate dust entrained in the air stream passing through the nozzle;dust collection means within the casing and beneath said filter means,the casing having a removable portion substantially flush with saidbottom surfaces for subsequent removal of collected dust; and nozzlebypass means in said casing through which air flows to the rotorunaffected by the surface to be cleaned when the resistance to air flowthrough the nozzle exceeds a predetermined level by reason of theconjunction of said surface with the nozzle whereby throughput of airthrough said rotor is maintained independent of air flow through saidnozzle; the over-all height of said cleaner head being substantiallyequal to the over-all height of said motor and attached rotor.

13. A vacuum cleaner as claimed in claim 12, wherein the nozzle bypassmeans includes a smoothly convergent duct adjacent said nozzle andleading from ambient atmosphere, the duct being directed on to thatportion of the surface to be cleaned which lies beneath the nozzle andentering the'nozzle at a point spaced from that surface so that airflowing through the duct becomes turbulent within the nozzle.

14. A vacuum cleaner as claimed in claim 13, wherein the duct enters thenozzle substantially centrally thereof 1 7 as considered in longitudinalvertical sections through the 2,128,525 cleaner head. 2,228,532 2,3 26,3 1 1 References Clted by the Exammer 2 337 936 UNITED STATES PATENTS 18Dyer 15-375 Opel 15-344 X Taylor 15--375 Sellers l5347 ROBERT N.MICHELL, Primary Examiner. WALTER A. SCHEEL, Examiner.

1. A VACUUM CLEANER COMPRISING A HANDLE AND A CLEANER HEAD ADAPTED TO BEPUSHED OVER A SURFACE TO BE CLEANED, SAID CLEANER HEAD HAVING A CASINGWITH AN UPPER SURFACE AND SUBSTANTIALLY FLAT BOTTOM SURFACES ADAPTED TOSLIDE OVER THE SURFACE TO BE CLEANED, A MOTOR IN SAID CASING, A BLOWEROF THE CROSS-FLOW TYPE IN SAID CASING ATTACHED AT ONE END TO THE SHAFTOF SAID MOTOR WITH SAID BLOWER HAVING A DRUM-SHAPED BLADED ROTOR, SAIDROTOR BEING VERTICALLY POSITIONED IN SAID CASING WHEREIN THELONGITUDINAL AXIS OF SAID BLOWER IS VERTICAL, A NOZZLE IN SAID CASINGADAPTED TO SLIDE OVER THE SURFACE TO BE CLEANED AND BEING CONNECTED TOTHE SUCTION SIDE OF SAID BLOWER, AN OUTLET IN THE UPPER PART OF SAIDCASING CONNECTED TO THE OUTLET OF SAID BLOWER AND BEING AT SUBSTANTIALLYTHE SAME HEIGHT AS THE END OF SAID BLOWER OPPOSITE SAID MOTOR SO THATTHE OVER-ALL HEIGHT OF SAID CLEANING HEAD IS SUBSTANTIALLY EQUAL TO THEOVER-ALL HEIGHT OF SAID MOTOR AND ATTACHED BLOWER, COLLECTION MEANS INSAID CLEANER HEAD FOR COLLECTING DUST FOR SUBSEQUENT REMOVAL FROM SAIDCLEANER HEAD, FILTER MEANS IN SAID CLEANER HEAD TO SEPARATE DUSTENTRAINED IN THE AIR PASSING THROUGH SAID NOZZLE, AND NOZZLE BYPASSMEANS THROUGH WHICH AIR FLOWS TO THE ROTOR UNAFFECTED BY THE SURFACE TOBE CLEANED WHEN RESISTANCE TO AIR FLOW THROUGH THE NOZZLE EXCEEDS APREDETERMINED LEVEL BY REASON OF THE CONJUNCTION OF SAID SURFACE TO BECLEANED WITH THE NOZZLE WHEREBY THROUGHPUT OF AIR THROUGH SAID ROTOR ISMAINTAINED INDEPENDENT OF AIR FLOW THROUGH SAID NOZZLE.